A plated material produced by providing a plating layer of, for example, tin (Sn) or a tin alloy, on an electroconductive base material, such as copper (Cu) or a copper alloy (hereinafter, appropriately referred to as base material), is known as a high performance conductor material having the excellent electroconductivity and mechanical strength of the base material, as well as the excellent electrical connectivity, corrosion resistance, and solderability of the plating layer. Thus, such plated materials are widely used in various terminals, connectors, and the like.
In recent years, since a fitting-type connector is multipolarized with advancement of electronic control, a considerable force is necessary for plugging a group of male terminals into/out of a group of female terminals. In particular, plugging-in/out such a connector is difficult in a narrow space such as the engine room of a vehicle, and it has been strongly demanded to reduce the force for plugging in/out such a connector.
In order to reduce the plugging-in/out force, the Sn plating layer on the surface of the connector terminal may be thinned to weaken contact pressure between the terminals. However, because the Sn plating layer is soft, a fretting phenomenon may occur between contact faces of the terminals, thereby causing inferior conduction between the terminals.
In the fretting phenomenon, the soft Sn plating layer on the surface of the terminal wears and is oxidized, becoming abrasion powder having large specific resistance, due to fine vibration between the contact faces of the terminals caused by vibration and changes in temperature. When this phenomenon occurs between the terminals, conduction between the terminals results in inferior. The lower the contact pressure between the terminals, the more the fretting phenomenon is apt to occur.
Patent Literature 1 describes a method of producing a fitting-type connection terminal, in which an underlying copper plating layer is formed on a base material of copper or a copper alloy, a tin plating layer is further formed on the surface thereof, then the face opposite to the sliding face in the fitting unit of the terminal is irradiated with a laser beam, so that the part corresponding to the beam spot of the laser in the sliding face is heated by heat transfer, and thereby a copper-tin alloy layer is formed at the interface between the tin plating layer and the underlying copper plating layer.
According to Patent Literature 1, it is believed that, under laser beam irradiation conditions that are capable of maintaining a thin tin plating layer, it is possible to decrease the plugging-in force of the terminal while maintaining the contact resistance stable; further, since the tin plating layer is not directly irradiated with the laser beam, the tin plating layer does not undergo a change by fusion, and the contact resistance is not deteriorated.
Patent Literature 2 describes a fitting-type male terminal having a tin plated layer provided on the surface of a tab of the fitting-type male terminal where plugging marks are formed on the surface of the tabular tab of the fitting-type male terminal when brought into elastic contact with protruding parts formed so as to sandwich the tab within the fitting unit of a fitting-type female terminal, wherein the vicinity of the connection mark at the end of the plugging mark is surface-treated to have a plating thickness that is at least larger than that of the area where the plugging mark is formed.
In this fitting-type male terminal, the contact site where the connection mark is formed has a plating layer that is capable of securing connection reliability, and the plating layer of the area where the plugging mark is formed in the front part of the contact site, is thin. Thus, it is believed to make it possible to achieve both the effect of reducing a plugging-in force and the connection reliability.    Patent Literature 1: JP-A-11-233228 (“JP-A” means unexamined published Japanese patent application)    Patent Literature 2: JP-A-2005-353352